Introduction: elements in an approach to human development. Three areas for constructive work on human development are much discussed: what are the values which should define and guide human development; what are causes and barriers for human development; and how can we operationalize a theorized approach (a package of concepts, values and explanatory theories) in terms of measurement, instruments and policy priorities. There are also three less discussed but essential counterpart areas of work. First, operationalization requires not just measurement but institutionalization, including establishing and sustaining a programme of research for action, and attracting and keeping the support of a body of researchers and potential users. Second, an ongoing research and policy programme of human development, and action on its findings, requires a basis of widespread public commitment and concern. Lastly, without rich observation and evidence, each of the required commitment, concern, ethical theory and positive theory is likely to be weak and insufficient. Table 3.1 highlights these two sets of areas: the left-hand column lists the already much discussed areas, and the right-hand column presents the less discussed but equally essential counterparts. A theory of human development needs thus to be more than only a theory in welfare economics or ethics. Amartya Sen's capability approach arose in response to the question of what is the appropriate space for evaluating people's advantage and the distribution of advantages ('equality of what?'). A human development theory or approach has further purposes besides evaluation and so requires additional types of information. Sen has extended his capability approach considerably, notably in Development as Freedom (1999), but it retains a welfare economics imprint. A human development theory should preferably be helpful in other roles, too: including for understanding behaviour and explaining agency and satisfactions; for mobilization of attention, concern and commitment; and for guidance in the processes of formulating, making and implementing public choices.